Running gear unit for a rail vehicle

ABSTRACT

A running gear unit for a rail vehicle, having a running gear frame body. The frame body includes two longitudinal beams and a transverse beam unit providing a structural connection between the longitudinal beams, such that a substantially H-shaped configuration is formed. Each longitudinal beam has a suspension interface section associated to a free end section of the longitudinal beam and forming a primary suspension interface for a primary suspension device. Each longitudinal beam has a pivot interface section associated to the primary suspension interface section and forming a pivot interface for a pivot arm. The primary suspension interface is configured to take a total resultant support force acting in the area of the free end section when the frame body is supported on the associated wheel unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national phase of International ApplicationNo. PCT/EP2013/061132 filed May 29, 2013, and claims priority toEuropean Patent Application No. 12170076.9 filed May 30, 2012, thedisclosures of which are hereby incorporated in their entirety byreference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a running gear unit for a rail vehiclecomprising a running gear frame body defining a longitudinal direction,a transverse direction and a height direction. The frame body comprisestwo longitudinal beams and a transverse beam unit providing a structuralconnection between the longitudinal beams in the transverse direction,such that a substantially H-shaped configuration is formed. Eachlongitudinal beam has a primary suspension interface section associatedto a free end section of the longitudinal beam and forming a primarysuspension interface for a primary suspension device connected to anassociated wheel unit. Furthermore, each longitudinal beam has a pivotinterface section associated to the primary suspension interface sectionand forming a pivot interface for a pivot arm connected to theassociated wheel unit. The primary suspension interface is configured totake a total resultant support force acting in the area of the free endsection when the frame body is supported on the associated wheel unit.The invention furthermore relates to a rail vehicle unit with a runninggear unit according to the invention.

Description of Related Art

Such a running gear frame is, for example, known from DE 41 36 926 A1(the entire disclosure of which is incorporated herein by reference).This running gear frame, due to its specific design of the support onthe wheel units (such as wheel pairs or wheels sets etc.) isparticularly well suited for the use in low floor vehicles, such astramways or the like. However, due to this support using a horizontallyarranged primary spring resting against a pillar element which isconsiderably retracted in the longitudinal direction with respect to thepivot interface, the running gear frame has a very complex, multiplybranched geometry. Hence, just like for many other structural componentsfor rail vehicles, the production of the running gear frame known fromDE 41 36 926 A1, not least due to its comparatively complex geometry, isperformed by welding sheet material. This production method, however,has the disadvantage that it requires a relatively large percentage ofmanual labor, which makes the production of running gear framescomparatively expensive.

Furthermore, on the one hand, the pillar element and the horizontallyarranged primary spring require comparatively much building space.Since, typically, the building space budget available in a running gear(for receiving the plurality of components required in modern railvehicles) is heavily restricted, such a configuration is less favorable.This is not least due to the fact that more effort has to be taken tofit all the necessary components into the limited building spaceavailable which, ultimately, adds to the overall cost of the vehicle. Inaddition, the pivot arm itself is of comparatively complex and heavydesign, thereby also adding to the overall complexity, the weight and,ultimately, to the overall cost of the vehicle.

SUMMARY OF THE INVENTION

Thus, it is the object of the present invention to provide a runninggear unit as described above, which does not show the disadvantagesdescribed above, or at least shows them to a lesser extent, and which,in particular, provides a space saving design which reduces the overalleffort and facilitates simple production of such running gear units.

The above objects are achieved starting from a running gear unitaccording to the preamble of claim 1 by the features of thecharacterizing part of claim 1.

The present invention is based on the technical teaching that a morespace saving design resulting in a more simple producibility can beaccomplished, if the primary suspension interface is configured suchthat the total resultant support force acting in the area of therespective free end (i.e. the total force resulting from all the supportforces acting via the primary suspension in the region the free end,when the running gear frame is supported on the wheel unit) is inclinedwith respect to the longitudinal direction and inclined with respect tothe height direction.

It should be noted that, unless stated otherwise in the following, allstatements with respect to inclination of the total resultant forcerefer to a static state with a rail vehicle standing on a straight leveltrack under its nominal load.

Such an inclination of the total resultant support force with respect toboth the longitudinal direction and the height direction, in particular,allows realization of very beneficial configurations in terms of therequired building space. In particular, compared to a configuration asknown from DE 41 36 926 A1, such an arrangement allows the primarysuspension device to move closer to the wheel unit, more preciselycloser to the axis of rotation of the wheel unit. This has not only theadvantage that the primary suspension interface also can be arrangedmore closely to the wheel unit, which clearly saves space in the centralpart of the running gear. Furthermore, in particular, the pivot armconnected to the wheel unit can be of smaller, more lightweight and lesscomplex design.

Furthermore, for example, such an inclined total resultant support forceyields the possibility to realize a connection between the pivot arm andthe frame body at the pivot interface which is both self adjusting underload (due to the components of the total resultant force acting in thelongitudinal direction and the height direction) while being easilydismounted in absence of the support load as it is described in greaterdetail in pending German patent application No. 10 2011 110 090.7 (theentire disclosure of which is incorporated herein by reference).

Finally, such a design has the advantage that, not least due to the factthat the interface section moves closer to the wheel unit, itfacilitates a switch to a more cost-effective automated production ofthe frame body using an automated casting process as will be explainedin further detail below.

Hence, according to one aspect, the present invention relates to arunning gear unit for a rail vehicle, comprising a running gear framebody defining a longitudinal direction, a transverse direction and aheight direction. The frame body comprises two longitudinal beams and atransverse beam unit providing a structural connection between saidlongitudinal beams in said transverse direction, such that asubstantially H-shaped configuration is formed. Each longitudinal beamhas a suspension interface section associated to a free end section ofsaid longitudinal beam and forming a primary suspension interface for aprimary suspension device connected to an associated wheel unit. Eachlongitudinal beam has a pivot interface section associated to theprimary suspension interface section and forming a pivot interface for apivot arm connected to the associated wheel unit. The primary suspensioninterface is configured to take a total resultant support force actingin the area of the free end section when the frame body is supported onthe associated wheel unit. The primary suspension interface isconfigured such that the total resultant support force is inclined withrespect to the longitudinal direction and inclined with respect to theheight direction.

Basically, the total resultant support force may have any desired andsuitable inclination with respect to the longitudinal direction and theheight direction. Preferably, the total resultant support force isinclined with respect to said height direction by a primary suspensionangle, the primary suspension angle ranging from 20° to 80°, preferablyfrom 30° to 70°, more preferably from 40° to 50°, since these values,among others, are particularly beneficial in terms of a space-savingdesign as well as a favorable introduction of support loads from thewheel unit via the primary suspension into the frame body.

Generally, any desired relation between the total resultant force andthe wheel unit, in particular its axis of wheel rotation, may be chosen.Preferably, the associated wheel unit is connected to the frame body viathe pivot arm pivotably linked to the pivot interface. The primarysuspension interface and the primary suspension device are arranged suchthat the total resultant support force intersects a wheel shaft of thewheel unit, in particular, an axis of wheel rotation of said wheelshaft. Such a configuration, among others, results in a particularlybeneficial introduction of support loads from the wheel unit into theprimary suspension and onwards into the frame body.

The primary suspension interface may have any desired shape. Forexample, one or more separate interface surfaces may be realized. Theseinterface surfaces may furthermore have any desired shape, for example,a section wise planar shape, a section wise curved shape as well as asection wise stepped shape etc.

With advantageous embodiments of the invention, the primary suspensioninterface defines a main interface plane, the main interface plane beingconfigured to take at least a major fraction of the total resultantsupport force. The main interface plane is inclined with respect to thelongitudinal direction and inclined with respect to the heightdirection. Preferably, the main interface plane is inclined with respectto the height direction by a main interface plane angle, the maininterface plane angle ranging from 20° to 80°, preferably from 30° to70°, more preferably from 40° to 50°. Furthermore, preferably, the maininterface plane is substantially parallel with respect to the transversedirection which leads to a configuration which is very simple tomanufacture and leads to an advantageous introduction of the forces intothe frame body.

Basically, any desired and suitable relative position may be selectedbetween the primary suspension interface and the pivot interface.However, preferably, the pivot interface section, in the longitudinaldirection, is arranged to be at least partially retracted behind acenter of the primary suspension interface, which results in a verysimple design of the end part of the longitudinal beam as a pillarsection. This is beneficial under many manufacturing aspects, inparticular, the suitability of the frame body for using an automatedcasting process. Furthermore, such a configuration is beneficial interms of the design of the pivot arm and the introduction of the supportloads into the frame body.

Typically, a center of a forward primary suspension interface and acenter of a rearward primary suspension interface of one of thelongitudinal beams, in the longitudinal direction, define a maximumprimary suspension interface center distance. Furthermore, typically, aforward pivot interface section is associated to the forward primarysuspension interface and defines a forward pivot axis for a forwardpivot arm, while a rearward pivot interface section is associated to therearward primary suspension interface and defines a rearward pivot axisfor a rearward pivot arm, the forward pivot axis and the rearward pivotaxis, in the longitudinal direction, defining a pivot axis distance.Preferably, the pivot axis distance is 60% to 105%, preferably 70% to95%, more preferably 80% to 85%, of the maximum primary suspensioninterface center distance. Such a configuration is particularlybeneficial in terms of the design of the pivot arm and the introductionof the support loads into the frame body.

Basically, the primary suspension unit and, consequently, the primarysuspension interface in may have any desired and suitable shape. Forexample, any desired type and/or number of primary spring elements maybe used in connection with an appropriate interface. With certainpreferred embodiments of the invention having a very simple design, theprimary suspension interface is configured as an interface for a singleprimary suspension device. Preferably, the primary suspension device isformed by a single primary suspension unit, which, further preferably,is formed by a single primary suspension spring, leading to a designwhich is very simple and easy to manufacture. Any type of primary springmay be used. Preferably, due to its compact and robust design, arubber-metal-spring unit is used for the primary spring.

The frame body, in general, may be produced in any desired manufacturingprocess. However, as mentioned above, the design of the interfacesection with an inclined total resulting support force and the closerproximity between the interface section and the wheel unit allows aswitch to a more cost-effective automated production of the frame bodyusing an automated casting process. This is not least a result of thefact that, which such a shift of the end part of the longitudinal beamcloser towards the wheel unit, this end part may be of less branchedand, hence, less complex design (compared to the solution known from DE41 36 926 A1), which is now suitable for such an automated castingprocess.

Hence, with preferred embodiments of the invention, the frame body isformed as a monolithically cast component made of a grey cast ironmaterial. Using grey cast iron has the advantage that it comprises aparticularly good flow capability during casting due to its high carboncontent and thus leads to a very high level of process reliability. Ithas turned out that, due to one or more of the geometric modificationsas outlined herein, a switch to grey cast iron was feasible allowing theproduction of such a comparatively large frame body of complex,generally three-dimensional geometry in conventional molding boxes ofautomated casting production lines. Consequently, production of theframe body is significantly simplified and rendered more cost effective.In fact, it has turned out that, compared to a conventional weldedrunning gear frame, a cost reduction by more than 50% may be achievedwith such an automated casting process.

A further advantage of the grey cast iron material is its improveddamping property compared to the steel material which is typically used.This is particularly advantageous with respect to reducing thetransmission of vibrations into the passenger compartment of a railvehicle.

The grey cast iron material can be any suitable grey cast iron material.Preferably, it is a so called nodular graphite iron cast material orspheroidal graphite iron (SGI) cast material. So called austemperedductile iron (ADI) cast material may also be used. Hence. EN-GJSmaterials as currently specified in European Norms EN 1563 (for SGImaterials) and EN 1564 (for ADI materials) may be used. Particularlysuitable materials are EN-GJS-400 materials (as specified in EuropeanNorm EN 1563), which provide a good compromise between strength,elongation at fracture and toughness. Preferably, EN-GJS-400-18U LT isused, which is characterized by advantageous toughness at lowtemperatures. Another preferred material would be EN-GJS-350-22-LT.

With further preferred embodiments of the invention providing acomparatively simple structure of the frame body well-suited for anautomated casting process, each longitudinal beam has an angled sectionassociated to the free end section, the angled section being arrangedsuch that the free end section forms a pillar section at least mainlyextending in the height direction. Furthermore, preferably, the pivotinterface section is integrated into the angled section. Integration ofthe pivot interface section into the angled section also provides anoticeable reduction in the complexity of the frame geometry whichfacilitates using a grey cast iron material for forming the frame bodyas a monolithically cast component (i.e. forming the frame body in asingle cast piece) in an automated casting process.

Integration of the pivot interface section into the angled section maybe achieved by any suitable geometry avoiding a split of the structurein separate branches (as it is known from the prior art structures),which the material flow would have to follow during casting. Preferably,the pivot interface section, in the longitudinal direction, is arrangedto be at least partially retracted behind the associated free endsection, thereby here simple manner achieving such an integration of thepivot interface section into the angled section.

With typical variants of the invention, a forward free end section and arearward free end section of one of the longitudinal beams, in thelongitudinal direction, define a maximum longitudinal beam length of thelongitudinal beam. Furthermore, typically, a forward pivot interfacesection is associated to the forward free end section and a rearwardpivot interface section is associated to the rearward free end section,the forward pivot interface section and the rearward pivot interfacesection, in the longitudinal direction, defining a maximum pivotinterface dimension of the longitudinal beam. Preferably, the maximumpivot interface dimension is 70% to 110%, preferably 80% to 105%, morepreferably 90% to 95%, of the maximum longitudinal beam length, therebyachieving a very compact design showing (if at all) only a comparativelymoderate longitudinal protrusion in the area at the pivot interface and,hence, yielding appropriate boundary conditions for optimized materialflow during casting which is essential in an automated casting process.

With certain embodiments of the invention showing a very beneficialdegree of integration of the pivot interface into the angled section, aforward pivot interface section associated to the forward free endsection defines a forward pivot axis for a forward pivot arm, while arearward pivot interface section associated to the rearward free endsection defines a rearward pivot axis for a rearward pivot arm. Theforward pivot axis and the rearward pivot axis, in the longitudinaldirection, define a pivot axis distance, the pivot axis distance being60% to 90%, preferably 70% to 80%, more preferably 72% to 78%, of themaximum longitudinal beam length.

It has turned out that, within the design specifications as outlinedherein, suitability for automated casting may be achieved for runninggear frame bodies having a considerable size in all three dimensions inspace, in particular, not only in the “horizontal” plane (i.e. the planeparallel to the longitudinal direction and the transverse direction) butalso in the height direction. Hence, with certain embodiments of theinvention, in the height direction, one of the longitudinal beams, in alongitudinally central section, defines a longitudinal beam undersideand a maximum central beam height of the longitudinal beam above thelongitudinal beam underside, while one of the free end sections of thelongitudinal beam defines a maximum beam height above the longitudinalbeam underside. The maximum beam height is 200% to 450%, preferably 300%to 400%, more preferably 370% to 380%, of the maximum central beamheight. Such a considerable height dimension of the pillar sectionfacilitates, among others, a modification of the arrangement of theprimary suspension unit (namely a switch from the known horizontalarrangement to an inclined arrangement) as has been explained above.

The transverse beam unit may be of any desired shape and design. Forexample, it may comprise one or more transverse beams interconnectingthe two longitudinal beams. Such a transverse beam may have any desiredcross-section. For example, such a transverse beam may have a generallybox shaped design with a closed or generally ring-shaped cross-section.However, many other types of transverse beams may be chosen. Forexample, a conventional I-beam shape may be chosen.

Preferably, the transverse beam unit comprises at least one transversebeam, the at least one transverse beam, in a sectional plane parallel tothe longitudinal direction and the height direction, defining asubstantially C-shaped cross section. Such an open design has theadvantage that (despite the general rigidity of the materials used) thetransverse beam is comparatively torsionally soft, i.e. shows acomparatively low resistance against torsional moments about thetransverse axis (compared to a closed, generally box shaped design ofthe transverse beam). This is particularly advantageous with respect tothe derailment safety of the running gear since the running gear frameitself is able to provide some torsional deformation tending to equalizethe wheel to rail contact forces on all four wheels.

Generally, any desired orientation of the substantially C-shaped crosssection may be chosen. This may be done, in particular, as a function ofthe amount and/or orientation of the bending loads to be taken up by thetransverse beam. Preferably, the substantially C-shaped cross section isarranged such that, in the longitudinal direction, it is open towards afree end of the frame body and, in particular, substantially closedtowards a center of the frame body. Such a configuration is particularlybeneficial if more than one transverse beams are used and a focus is tobe put on a low torsional rigidity of the transverse beam unit.

The substantially C-shaped cross section may be arranged at anytransverse position in the transverse beam unit. Preferably, theC-shaped cross section, in the transverse direction, extends over atransversally central section of the transverse beam unit, since at thislocation, a particularly beneficial influence on the torsional rigidityof the transverse beam unit may be achieved.

The substantially C-shaped cross section may extend over the entireextension of the transverse beam unit in the transverse direction.Preferably, the substantially C-shaped cross section extends, in thetransverse direction, over a transverse dimension, the transversedimension being at least 50%, preferably at least 70%, more preferably80% to 95%, of a transverse distance between longitudinal center linesof the longitudinal beams in the area of the transverse beam unit. Bythis means a particularly advantageous torsional rigidity may beachieved even with such a grey cast iron frame body.

With preferred embodiments of the invention the at least one transversebeam is a first transverse beam and the transverse beam unit comprises asecond transverse beam. Such a configuration has the advantage that,compared to a configuration with one single transverse beam, themechanical properties may be more easily tuned to the requirements ofthe specific running gear. Preferably, the first transverse beam and thesecond transverse beam are substantially symmetric with respect to aplane of symmetry parallel to the transverse direction and the heightdirection, thereby providing identical running properties irrespectiveof the direction of travel.

Moreover, with transverse beams having C-shaped cross sections the opensides of which are facing away from each other, the increase in theoverall torsional rigidity of the transverse beam unit resulting fromthe fact that two transverse beams are used may be kept comparativelylow. This is due to the fact that the closed sides of the two transversebeams (in the longitudinal direction) are located comparativelycentrally within the transverse beam unit, such that their contributionto the torsional resistance moment is comparatively low.

Furthermore, preferably, the first transverse beam and the secondtransverse beam are separated, in the longitudinal direction, by a gaphaving a longitudinal gap dimension. Such a gap between the twotransverse beams has in the advantage that the bending resistance in theplane of main extension of the two beams is increased without adding tothe mass of the frame body, such that a comparatively lightweightconfiguration is achieved. Furthermore, such a gap is readily availablefor receiving other components of the running gear, which isparticularly beneficial in modern rail vehicles with their severeconstraints regarding the building space available.

The longitudinal gap dimension may be selected as desired. Preferably,the longitudinal gap dimension is 70% to 120%, preferably 85% to 110%,more preferably 95% to 105%, of a minimum longitudinal dimension of oneof the transverse beams in the longitudinal direction, thereby achievinga well-balanced configuration showing both, comparatively low torsionalrigidity (about the transverse direction) and comparatively high bendingrigidity (about the height direction).

The first and second transverse beam may be of any desired generalshape. Preferably, the first transverse beam and the second transversebeam each define a transverse beam center line, at least one of thetransverse beam center lines, at least section wise, having a generallycurved or polygonal shape in a first plane parallel to the longitudinaldirection and the transverse direction and/or a second plane parallel tothe transverse direction and the height direction. Such generally curvedor polygonal shapes of the transverse beam center lines have theadvantage that the shape of the transverse beam may be adapted to thedistribution of the loads acting on the respective transverse beamresulting in a comparatively smooth distribution of the stresses withinthe transverse beam and, ultimately, in a comparatively light weight andstress optimized frame body.

With certain preferred embodiments of the invention, the transverse beamunit is a locally waisted unit, in particular a centrally waisted unit,the transverse beam unit having a waisted section defining a minimumlongitudinal dimension of the transverse beam unit in the longitudinaldirection. Such a waisted configuration, among others, is advantageousin terms of the low torsional rigidity of the frame body about thetransverse direction.

Generally, the extent of the waist may be chosen as a function of themechanical properties, in particular, the torsional rigidity, to beachieved. Preferably, the minimum longitudinal dimension of thetransverse beam unit is 40% to 90%, preferably 50% to 80%, morepreferably 60% to 70%, of a maximum longitudinal dimension of thetransverse beam unit in the longitudinal direction, the maximumlongitudinal dimension, in particular, being defined at a junction ofthe transverse beam unit and one of the longitudinal beams.

With advantageous embodiments of the invention the free and section, ina section facing away from the primary spring interface, forms a stopinterface for a stop device. Preferably, the stop device is a rotationalstop device and/or longitudinal stop device, which may also be adaptedto form a traction link between the frame body and a component, inparticular a bolster or a wagon body, supported on the frame body. Itwill be appreciated that such a configuration is particularly beneficialsince it provides a high degree of functional integration leading to acomparatively lightweight overall design.

The present invention furthermore relates to a rail vehicle unitcomprising a first running gear unit according to the inventionsupported on two wheel units via primary spring units and pivot armsconnected to a frame body of the first running gear unit to form a firstrunning gear. A further rail vehicle component may be supported on theframe body, the rail vehicle component, in particular, being a bolsteror a wagon body.

It will be appreciated that, according to a further aspect of thepresent invention, the frame body may be formed as a standardizedcomponent which may be used for different types of running gears.Customization of the respective frame body to the specific type ofrunning gear type may be achieved by additional type specific componentsmounted to the standardized frame body. Such an approach is highlyadvantageous in terms of its commercial impact. This is due to the factthat, in addition to the considerable savings achieved due to theautomated casting process, only one single type of frame body has to bemanufactured, which brings along a further considerable reduction incosts.

Hence, preferably, the rail vehicle unit comprises a second running gearframe according to the invention supported on two wheel units viaprimary spring units and pivot arms connected to a frame body of thesecond running gear frame to form a second running gear. The firstrunning gear may be a driven running gear comprising a drive unit, whilethe second running gear may be a non-driven running gear having a nodrive unit. Preferably, at least the frame body of the first runninggear frame and the frame body of the second running gear frame aresubstantially identical.

It should be noted in this context that customization of the runninggear to a specific type or function on the basis of identical framebodies is not limited to a differentiation in terms of driven andnon-driven running gears. Any other functional components may be used toachieve a corresponding functional differentiation between such runninggears on the basis of standardized identical frame bodies.

Further embodiments of the present invention will become apparent fromthe dependent claims and the following description of preferredembodiments which refers to the appended figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a part of a preferred embodiment of arail vehicle according to the present invention with a preferredembodiment of a running gear unit according to the present invention;

FIG. 2 is a schematic perspective view of a frame body of the runninggear unit of FIG. 1;

FIG. 3 is a schematic sectional view of the frame body of FIG. 2 alongline III-III of FIG. 1.

FIG. 4 is a schematic frontal view of the frame body of FIG. 2.

FIG. 5 is a schematic sectional view of a part of the running gear unitalong line V-V of FIG. 1.

FIG. 6 is a schematic top view of the running gear unit of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1 to 6 a preferred embodiment of a rail vehicle101 according to the present invention comprising a preferred embodimentof a running gear 102 according to the invention will now be describedin greater detail. In order to simplify the explanations given below, anxyz-coordinate system has been introduced into the Figures, wherein (ona straight, level track T) the x-axis designates the longitudinaldirection of the rail vehicle 101, the y-axis designates the transversedirection of the rail vehicle 101 and the z-axis designates the heightdirection of the rail vehicle 101 (the same, of course, applies for therunning gear 102). It will be appreciated that all statements made inthe following with respect to the position and orientation of componentsof the rail vehicle, unless otherwise stated, refer to a staticsituation with the rail vehicle 101 standing on a straight level trackunder nominal loading.

The vehicle 101 is a low floor rail vehicle such as a tramway or thelike. The vehicle 101 comprises a wagon body 101.1 supported by asuspension system on the running gear 102. The running gear 102comprises two wheel units in the form of wheel sets 103 supporting arunning gear frame 104 via a primary spring unit 105. The running gearframe 104 supports the wagon body via a secondary spring unit 106.

The running gear frame 104 has a frame body 107 comprising twolongitudinal beams 108 and a transverse beam unit 109 providing astructural connection between the longitudinal beams 108 in thetransverse direction, such that a substantially H-shaped configurationis formed. Each longitudinal beam 108 has two free end sections 108.1and a central section 108.2. The central section 108.2 is connected tothe transverse beam unit 109 while the free end sections 108.1 form aprimary suspension interface 110 for a primary suspension device 105.1of the primary suspension unit 105 connected to the associated wheelunit 103. In the present example, a compact and robustrubber-metal-spring is used for the primary spring device 105.1.

Each longitudinal beam 108 has an angled section 108.3 associated to oneof the free end sections 108.1. Each angled section 108.3 is arrangedsuch that the free end section 108.1 forms a pillar section mainlyextending in the height direction. Hence, basically, the frame body 107has a comparatively complex, generally three-dimensional geometry.

Each longitudinal beam 108 has a pivot interface section 111 associatedto the free end section 108.1. The pivot interface section 111 forms apivot interface for a pivot arm 112 rigidly connected to a wheel setbearing unit 103.1 of the associated wheel unit 103. The pivot arm 112is pivotably connected to the frame body 107 via a pivot bolt connection113. The pivot bolt connection 113 comprises a pivot bolt 113.1 defininga pivot axis 113.2. The bolt 113.1 is inserted into matching recesses ina forked end of the pivot arm 112 and a pivot interface recess 111.1 ina lug 111.2 of the pivot interface section 111 (the lug 111.2 beingreceived between the end parts of the pivot arm 112).

To reduce the complexity of the frame body 107, the respective pivotinterface section 111 is integrated into to the angled section 108.3 ofthe longitudinal beams 108, such that, nevertheless, a very compactarrangement is achieved. More precisely, integration of the pivotinterface section 111 into the angled section 108.3 leads to acomparatively smooth, unbranched geometry of the frame body.

This compact, smooth and unbranched arrangement, among others, makes itpossible to form the frame body 107 as a monolithically cast component.More precisely, the frame body 107 is formed as a single piece cast inan automated casting process from a grey cast iron material. The greycast iron material has the advantage that it comprises a particularlygood flow capability during casting due to its high carbon content andthus leads to a very high level of process reliability.

Casting is done in conventional molding boxes of an automated castingproduction line. Consequently, production of the frame body 107 issignificantly simplified and rendered more cost effective than inconventional solutions with welded frame bodies. In fact, it has turnedout that (compared to a conventional welded frame body) a cost reductionby more than 50% may be achieved with such an automated casting process.

The grey cast iron material used in the present example is a so callednodular graphite iron cast material or spheroidal graphite iron (SGI)cast material as currently specified in European Norm EN 1563. Moreprecisely, a material such as EN-GJS-400-18U LT is used, which providesa good compromise between strength, elongation at fracture andtoughness, in particular at low temperatures. Obviously, depending onthe mechanic requirements on the frame body, any other suitable castmaterial as outlined above may be used.

To achieve proper integration of the pivot interface section 111 intothe angled section 108.3, the respective pivot interface section 111, inthe longitudinal direction (x-axis), is arranged to be retracted behindthe associated free end section 108.1.

In the present example, a forward free end section 108.1 and a rearwardfree end section 108.1 of each longitudinal beam 108, in thelongitudinal direction, define a maximum longitudinal beam lengthL_(LB,max) of the longitudinal beam 108. Furthermore, a forward pivotinterface section 111 (associated to the forward free end section 108.1)and a rearward pivot interface section 111 (associated to the rearwardfree end section 108.1), in the longitudinal direction, define a maximumpivot interface dimension L_(PI,max) of the longitudinal beam 108.

In the present example, the maximum pivot interface dimension L_(PI,max)is about 92% of the maximum longitudinal beam length L_(LB,max), therebyachieving a very compact design showing no longitudinal protrusion inthe area at the pivot interface 111 and, hence, yielding appropriateboundary conditions for optimized material flow during casting which isessential in the automated casting process used.

Furthermore, the forward pivot axis 113.2 (for the forward pivot arm112) and the rearward pivot axis 113.2 (for the rearward pivot arm 112),in the longitudinal direction, define a pivot axis distance L_(PA) beingabout 76% of the maximum longitudinal beam length L_(LB,max).

The frame body 107 of the present embodiment is suitable for automatedcasting despite its considerable size in all three dimensions (x,y,z) inspace, in particular, its considerable size not only in the “horizontal”plane (i.e. the xy-plane) but also its considerable size in the heightdirection (z-axis). More precisely, as can be seen from FIG. 3, in theheight direction, the longitudinally central section 108.2 defines alongitudinal beam underside and a maximum central beam heightH_(LBC,max) of the longitudinal beam 108 above the longitudinal beamunderside, while the free end sections 108.1 define a maximum beamheight H_(LB,max) above the longitudinal beam underside. Despite thefact that the maximum beam height H_(LB,max) of the present embodimentis as high as about 380% of the maximum central beam height H_(LBC,max),the frame body 107 may be cast as a single monolithic component.

According to a further aspect of the present invention (as can be seen,in particular, from FIG. 5) a considerable reduction in the buildingspace (required for frame body 107 within the running gear 102) isaccomplished in that the primary suspension interface 110 is configuredsuch that the total resultant support force F_(TRS) acting in the areaof the respective free end 108.1 (i.e. the total force resulting fromall the support forces acting via the primary suspension 105 in theregion the free end 108.1, when the running gear frame 104 is supportedon the wheel unit 103) is substantially parallel with respect to thexz-plane, while in being inclined with respect to the longitudinaldirection (x-axis) by a primary suspension angle α_(PSF,x) and inclinedwith respect to the height direction (z-axis) by a complementary primarysuspension angleα_(PSF,z)=90°−α_(PSF,x).  (1)

Such an inclination of the total resultant support force F_(TRS),compared to a configuration as known from DE 41 36 926 A1, allows theprimary suspension device 105.1 to move closer to the wheel set 103,more precisely closer to the axis of rotation 103.2 of the wheel set103. This has not only the advantage that the primary suspensioninterface 110 also can be arranged more closely to the wheel unit, whichclearly saves space in the central part of the running gear 102.Furthermore, the pivot arm 112 connected to the wheel set bearing unit103.1 can be of smaller, more lightweight and less complex design.

Furthermore, such an inclined total resultant support force F_(TRS)yields the possibility to realize a connection between the pivot arm 112and the frame body 107 at the pivot interface 111 which is both selfadjusting under load (due to the components of the total resultant forceF_(TRS) acting in the longitudinal direction and the height direction)while being easily dismounted in absence of the support load F_(TRS) asit is described in greater detail in pending German patent applicationNo. 10 2011 110 090.7 (the entire disclosure of which is incorporatedherein by reference).

Finally, such a design has the advantage that, not least due to the factthat the primary suspension interface section 110 moves closer to thewheel set 103, it further facilitates automated production of the framebody 107 using an automated casting process.

Although, basically, the total resultant support force F_(TRS) may haveany desired and suitable inclination with respect to the longitudinaldirection and the height direction, in the present example, the totalresultant support force F_(TRS) is inclined with respect to thelongitudinal direction by a primary suspension angle α_(PSF,x)=45°.Consequently, the total resultant support force is inclined with respectto the height direction by a complementary primary suspension angleα_(PSF,z)=90°−α_(PSF,x)=45°. Such an inclination provides a particularlycompact and, hence, favorable design. Furthermore, it also provides anadvantageous introduction of the support loads F_(TRS) from the wheelset 103 into the frame body 107. Finally, as a consequence, the pillarsection or end section 108.1 may be formed in a slightly forward leaningconfiguration which is favorable in terms of facilitating cast materialflow and, hence, use of an automated casting process.

As may be further seen from FIG. 5, the primary suspension interface 110and the primary suspension device 105.1 are arranged such that the totalresultant support force F_(TRS) intersects a wheel set shaft 103.3 ofthe wheel set 103, leading to a favorable introduction of the supportloads from the wheel set 103 into the primary suspension device 105.1and onwards into the frame body 107. More precisely, the total resultantsupport force F_(TRS) intersects the axis of wheel rotation 103.2 of thewheel shaft 103.3.

Such a configuration, among others, leads to a comparatively short leverarm of the total resultant support force F_(TRS) (for example, a leverarm A_(TRS) at the location of the pivot bolt 113.1) and, hence,comparatively low bending moments acting in the longitudinal beam 108,which, in turn, allows a more lightweight design of the frame body 107.

A further advantage of the configuration as outlined above is the factthat the pivot arm 112 may have a very simple and compact design. Moreprecisely, in the present example, the pivot arm 112 integrating thewheel set bearing unit 103.1, apart from the forked end section(receiving the pivot bolt 113.1) simply has to provide a correspondingsupport surface for the primary spring device 105.1 located close to theouter circumference of the wheel set bearing unit 103.1. Hence, comparedto known configurations, no complex arms or the like are necessary forintroducing the support forces into the primary spring device 105.1.

Although, basically, the primary suspension interface 110 may have anydesired shape, in the present example, the primary suspension interface110 is a simple planar surface 110.1 laterally flanked by twoprotrusions 110.2 (against which mating surfaces of the primarysuspension device 105.1 rest, among others, for centering purposes). Theplanar surface 110.1 defines a main interface plane configured to take amajor fraction of the total resultant support force F_(TRS).

The main interface plane 110.1 is configured to be substantiallyperpendicular to the total resultant support force F_(TRS) as well assubstantially parallel to the transverse direction (y-axis). As aconsequence, the main interface plane 110.1 is inclined with respect tothe longitudinal direction and inclined with respect to the heightdirection. More precisely, the main interface plane 110.1 is inclinedwith respect to the height direction by a main interface plane angleα_(MIP,z)=90°−α_(PSF,z)=α_(PSF,x).  (2)

Hence, in the present case, the main interface plane 110.1 is inclinedwith respect to the height direction by a main interface plane angleα_(MIP,z)=45°.

To achieve the slightly forwardly leaning configuration of the free endsection 108.1 and its advantages as described above, in the presentexample, the pivot interface section 111, in the longitudinal direction,is retracted behind a center 110.3 of the primary suspension interface110. To this end, in the present embodiment, the pivot axis distanceL_(PA) is 82% of a primary suspension interface center distance L_(PSIC)defined (in the longitudinal direction) by the centers 110.3 of aforward primary suspension interface 110 and a rearward primarysuspension interface 110 of the longitudinal beams 108.

The transverse beam unit 109 comprises two transverse beams 109.1, whichare arranged to be substantially symmetric to each other with respect toa plane of symmetry parallel to the yz-plane and arranged centrallywithin the frame body 107. The transverse beams 109.1 (in thelongitudinal direction) are separated by a gap 109.5.

As can be seen from FIG. 3, each transverse beam 109.1, in a sectionalplane parallel to the xz-plane, has a substantially C-shaped crosssection with an inner wall 109.2, an upper wall 109.3, and a lower wall109.4. The C-shaped cross section is arranged such that, in thelongitudinal direction, it is open towards the (more closely located)free end of the frame body 107, while it is substantially closed by theinner wall 109.2 located adjacent to the center of the frame body 107.In other words, the open sides of the transverse beams 109.1 are facingaway from each other.

Such an open design of the transverse beam 109.1 has the advantage that(despite the general rigidity of the materials used) not only theindividual transverse beam 109.1 is comparatively torsionally soft, i.e.shows a comparatively low resistance against torsional moments about thetransverse y-axis (compared to a closed, generally box shaped design ofthe transverse beam). The same applies to the transverse beam unit 109as a whole, since the inner walls 109.2 (in the longitudinal direction)are located comparatively centrally within the transverse beam unit 109,such that their contribution to the torsional resistance moment aboutthe transverse y-axis is comparatively low.

Furthermore, the gap 109.5, in a central area of the frame body 107, hasa maximum longitudinal gap dimension L_(G,max), which is about 100% of aminimum longitudinal dimension L_(TB,min) of one of the transverse beams109.1 in the longitudinal direction (in the central area of the framebody 107). The gap 109.5 has the advantage that the bending resistancein the plane of main extension of the two transverse beams 109.1(parallel to the xy-plane) is increased without adding to the mass ofthe frame body 107, such that a comparatively lightweight configurationis achieved.

Furthermore, the gap 109.5 is readily available for receiving othercomponents of the running gear 102 (such as a transverse damper 114 asshown in FIG. 6), which is particularly beneficial in modern railvehicles with their severe constraints regarding the building spaceavailable.

The C-shaped cross section extends over a transversally central sectionof the transverse beam unit 109, since, at this location, a particularlybeneficial influence on the torsional rigidity of the transverse beamunit is achieved. In the present embodiment, the substantially C-shapedcross section extends over the entire extension of the transverse beamunit in the transverse direction (i.e. from one longitudinal beam 108 tothe other longitudinal beam 108). Hence, in the present example, theC-shaped cross section extends over a transverse dimension W_(TBC),which is 85% of a transverse distance W_(LBC) between longitudinalcenter lines 108.4 of the longitudinal beams 108 in the area of thetransverse beam unit 109. By this means a particularly advantageoustorsional rigidity may be achieved even with such a grey cast iron framebody 107.

As far as the extension in the transverse direction is concerned, thesame (as for the C-shaped cross-section) also applies to the extensionof the gap 109.5. Furthermore, it should be noted that the longitudinalgap dimension doesn't necessarily have to be the same along thetransverse direction. Any desired gap width may be chosen as needed.

In the present example, each transverse beam 109.1 defines a transversebeam center line 109.6, which has a generally curved or polygonal shapein a first plane parallel to the xy-plane and in a second plane parallelto the yz-plane. Such generally curved or polygonal shapes of thetransverse beam center lines 109.6 have the advantage that the shape ofthe respective transverse beam 109.1 is adapted to the distribution ofthe loads acting on the respective transverse beam 109.1 resulting in acomparatively smooth distribution of the stresses within the respectivetransverse beam 109.1 and, ultimately, in a comparatively lightweightand stress optimized frame body 107.

As a consequence, as can be seen from FIGS. 2 and 6, the transverse beamunit 109 is a centrally waisted unit with a waisted central section109.7 defining a minimum longitudinal dimension of the transverse beamunit L_(TBU,min) (in the longitudinal direction) which, in the presentexample, is 65% of a maximum longitudinal dimension of the transversebeam unit L_(TBU,min) (in the longitudinal direction). This maximumlongitudinal dimension, in the present example, is defined at thejunction of the transverse beam unit 109 and the longitudinal beams 108.

Generally, the extent of the waist of the transverse beam unit 109 maybe chosen as a function of the mechanical properties of the frame body107 (in particular, the torsional rigidity of the frame body 107) to beachieved. In any case, with the transverse beam unit design as outlinedherein, a well-balanced configuration is achieved showing both,comparatively low torsional rigidity (about the transverse direction)and comparatively high bending rigidity (about the height direction).This configuration is particularly advantageous with respect to thederailment safety of the running gear 102 since the running gear frame104 is able to provide some torsional deformation tending to equalizethe wheel to rail contact forces on all four wheels of the wheel sets103.

And can be further seen from FIGS. 3 and 6, in the present example, thefree end section 108.1, in a section facing away from the primary springinterface 110, forms a stop interface for a stop device 115. The stopdevices 115 integrate the functionality of a rotational stop device anda longitudinal stop device for the wagon body 101.1. Furthermore, thestop devices 115 also are adapted to form a traction link between theframe body 107 and the wagon body 101.1 supported on the frame body 107.It will be appreciated that such a configuration is particularlybeneficial since it provides a high degree of functional integrationleading to a comparatively lightweight overall design.

As can be seen from FIG. 1, the wagon body 101.1 (more precisely, eitherthe same part of the wagon body 101.1 also supported on the firstrunning gear 102 or another part of the wagon body 101) is supported ona further, second running gear 116. The second running gear 116 isidentical to the first running the 102 in all the parts described above.However, while the first running gear 102 is a driven running gear witha drive unit (not shown) mounted to the frame body 107, the secondrunning gear 116 is a non-driven running gear, having no such drive unitmounted to the frame body 107.

Hence, according to a further aspect of the present invention, the framebody 107 forms a standardized component which used for both, the firstrunning gear 102 and the second running gear, i.e. different types ofrunning gear. Customization of the respective frame body 107 to thespecific type of running gear type may be achieved by additional typespecific components mounted to the standardized frame body 107. Such anapproach is highly advantageous in terms of its commercial impact. Thisis due to the fact that, in addition to the considerable savingsachieved due to the automated casting process, only one single type offrame body 107 has to be manufactured, which brings along a furtherconsiderable reduction in costs.

It should again be noted in this context that customization of therunning gear 102, 116 to a specific type or function on the basis ofidentical frame bodies 107 is not limited to a differentiation in termsof driven and non-driven running gears. Any other functional components(such as e.g. specific types of brakes, tilt systems, rolling supportsystems, etc.) may be used to achieve a corresponding functionaldifferentiation between such running gears on the basis of standardizedidentical frame bodies 107.

Although the present invention, in the foregoing, only has beendescribed in the context of running gears with inboard wheelsetbearings, it should be noted that the present invention may also be usedin the context of running gears with outboard wheelset bearings. Thiswill require only slight modifications of the running gear frame, inparticular, the longitudinal beams, location of components such asmagnetic brakes etc. for adaptation to different track gauges.

Although the present invention in the foregoing has only a described inthe context of low-floor rail vehicles, it will be appreciated, however,that it may also be applied to any other type of rail vehicle in orderto overcome similar problems with respect to a simple solution forreducing the manufacturing effort.

The invention claimed is:
 1. A running gear unit comprising: a runninggear frame body defining a longitudinal direction, a transversedirection and a height direction; said frame body comprising twolongitudinal beams and a transverse beam unit providing a structuralconnection between said longitudinal beams in said transverse direction,such that a substantially H-shaped configuration is formed, eachlongitudinal beam having a suspension interface section associated to afree end section of said longitudinal beam and forming a primarysuspension interface for a primary suspension device connected to anassociated wheel unit; each longitudinal beam having a pivot interfacesection associated to said primary suspension interface section andforming a pivot interface for a pivot arm connected to said associatedwheel unit; said primary suspension interface being configured to take atotal resultant support force acting in the area of said free endsection when said frame body is supported on said associated wheel unit;wherein said primary suspension interface is configured such that saidtotal resultant support force is inclined with respect to saidlongitudinal direction and inclined with respect to said heightdirection, said primary suspension interface defines a main interfaceplane; said main interface plane being configured to take at least amajor fraction of said resultant support force; said main interfaceplane being inclined with respect to said longitudinal direction andinclined with respect to said height direction; said main interfaceplane being inclined with respect to said height direction by a maininterface plane angle, said main interface plane angle ranging from 40°to 50°; and said main interface plane being substantially parallel withrespect to said transverse direction.
 2. The running gear unit accordingto claim 1, wherein, said total resultant support force is inclined withrespect to said height direction by a primary suspension angle; saidprimary suspension angle ranging from 20° to 80°.
 3. The running gearunit according to claim 1, wherein, said associated wheel unit isconnected to said frame body via said pivot arm pivotably linked to saidpivot interface; said primary suspension interface and said primarysuspension device being configured such that said total resultantsupport force intersects a wheel shaft of said wheel unit.
 4. Therunning gear unit according to claim 1, wherein, said pivot interfacesection, in said longitudinal direction, is arranged to be at leastpartially retracted behind a center of said primary suspensioninterface; a center of a forward primary suspension interface and acenter of a rearward primary suspension interface of one of saidlongitudinal beams, in said longitudinal direction, defining a maximumprimary suspension interface center distance; a forward pivot interfacesection being associated to said forward primary suspension interfaceand defining a forward pivot axis for a forward pivot arm; a rearwardpivot interface section being associated to said rearward primarysuspension interface and defining a rearward pivot axis for a rearwardpivot arm; said forward pivot axis and said rearward pivot axis, in saidlongitudinal direction, defining a pivot axis distance; said pivot axisdistance being 60% to 105% of said maximum primary suspension interfacecenter distance.
 5. The running gear unit according to claim 1, wherein,said primary suspension interface is configured as an interface for asingle primary suspension device; said primary suspension device beingformed by a single primary suspension unit; said primary suspension unitbeing formed by a single primary suspension spring.
 6. The running gearunit according to claim 1, wherein, said frame body is formed as amonolithically cast component made of a grey cast iron material; saidframe body being made of a spheroidal graphite iron cast material; saidspheroidal graphite iron cast material being one of EN-GJS-400-18U LTand EN-GJS-350-22-LT.
 7. The running gear unit according to claim 1,wherein, each longitudinal beam has an angled section associated to saidfree end section; said angled section being configured such that saidfree end section (108.1) forms a pillar section at least mainlyextending in said height direction: said pivot interface section beingassociated to said angled section; said pivot interface section beingintegrated into to said angled section.
 8. The running gear unitaccording to claim 1, wherein said pivot interface section, in saidlongitudinal direction, is arranged to be at least partially retractedbehind said associated free end section; a forward free end section anda rearward free end section of one of said longitudinal beams, in saidlongitudinal direction, defining a maximum longitudinal beam length ofsaid longitudinal beam; a forward pivot interface section associated tosaid forward free end section defining a forward pivot axis for aforward pivot arm; a rearward pivot interface section associated to saidrearward free end section defining a rearward pivot axis for a rearwardpivot arm; said forward pivot axis and said rearward pivot axis, in saidlongitudinal direction, defining a pivot axis distance; said pivot axisdistance being 60% to 90% of said maximum longitudinal beam length. 9.The running gear unit according to claim 1, wherein, in said heightdirection, one of said longitudinal beams, in a longitudinally centralsection, defines a longitudinal beam underside and a maximum centralbeam height of said longitudinal beam above said longitudinal beamunderside, and one of said free end sections of said longitudinal beamdefines a maximum beam height above said longitudinal beam underside;said maximum beam height being 200% to 450% of said maximum central beamheight.
 10. The running gear unit according to claim 1, wherein, saidtransverse beam unit comprises at least one transverse beam; said atleast one transverse beam, in a sectional plane parallel to saidlongitudinal direction and said height direction, defining asubstantially C-shaped cross section; said substantially C-shaped crosssection being arranged such that, in said longitudinal direction, it isopen towards a free end of said frame body and substantially closedtowards a center of said frame body; said substantially C-shaped crosssection extending, in said transverse direction, over a transversallycentral section of said transverse beam unit; said substantiallyC-shaped cross section extending, in said transverse direction, over atransverse dimension, said transverse dimension being at least 50% of atransverse distance between longitudinal center lines of saidlongitudinal beams in the area of said transverse beam unit.
 11. Therunning gear unit according to claim 10, wherein, said at least onetransverse beam is a first transverse beam and said transverse beam unitcomprises a second transverse beam; said first transverse beam and saidsecond transverse beam being substantially symmetric with respect to aplane of symmetry parallel to said transverse direction and said heightdirection; said first transverse beam and said second transverse beambeing separated, in said longitudinal direction, by a gap having alongitudinal gap dimension; said longitudinal gap dimension being 70% to120% of a minimum longitudinal dimension of one of said transverse beamsin said longitudinal direction; said first transverse beam and saidsecond transverse beam each defining a transverse beam center line, atleast one of said transverse beam center lines, at least section wise,having a generally curved or polygonal shape in a first plane parallelto said longitudinal direction and said transverse direction or a secondplane parallel to said transverse direction and said height direction.12. The running gear unit according to claim 1, wherein, said transversebeam unit is a locally waisted unit; said transverse beam unit having awaisted section defining a minimum longitudinal dimension of saidtransverse beam unit in said longitudinal direction; said minimumlongitudinal dimension of said transverse beam unit being 40% to 90% ofa maximum longitudinal dimension of said transverse beam unit (109) insaid longitudinal direction, said maximum longitudinal dimension beingdefined at a junction of said transverse beam unit and one of saidlongitudinal beams.
 13. The running gear unit according to claim 1,wherein, said free end section, in a section facing away from a primaryspring interface, forms a stop interface for a stop device; said stopdevice being a rotational stop device or longitudinal stop device; saidstop device being adapted to form a traction link between said framebody and a component.
 14. A rail vehicle unit, comprising a firstrunning gear unit according to claim 1 supported on two wheel units viaprimary spring units and pivot arms connected to a frame body of saidfirst running gear unit to form a first running gear; a rail vehiclecomponent being supported on said frame body, said rail vehiclecomponent being a bolster or a wagon body; said rail vehicle unitcomprising a second running gear unit supported on two wheel units viaprimary spring units and pivot arms connected to a frame body of saidsecond running gear unit to form a second running gear; said firstrunning gear being a driven running gear comprising a drive unit, saidsecond running gear being a non-driven running gear having a no driveunit, at least said frame body of a first running gear frame and saidframe body of a second running gear frame being substantially identical.15. A running gear unit comprising: a running gear frame body defining alongitudinal direction, a transverse direction and a height direction;said frame body comprising two longitudinal beams and a transverse beamunit providing a structural connection between said longitudinal beamsin said transverse direction, such that a substantially H-shapedconfiguration is formed, each longitudinal beam having a suspensioninterface section associated to a free end section of said longitudinalbeam and forming a primary suspension interface for a primary suspensiondevice connected to an associated wheel unit; each longitudinal beamhaving a pivot interface section associated to said primary suspensioninterface section and forming a pivot interface for a pivot armconnected to said associated wheel unit; said primary suspensioninterface being configured to take a total resultant support forceacting in the area of said free end section when said frame body issupported on said associated wheel unit; wherein said primary suspensioninterface is configured such that said total resultant support force isinclined with respect to said longitudinal direction and inclined withrespect to said height direction, said pivot interface section, in saidlongitudinal direction, is arranged to be at least partially retractedbehind a center of said primary suspension interface; a center of aforward primary suspension interface and a center of a rearward primarysuspension interface of one of said longitudinal beams, in saidlongitudinal direction, defining a maximum primary suspension interfacecenter distance; a forward pivot interface section being associated tosaid forward primary suspension interface and a forward pivot axis for aforward pivot arm; a rearward pivot interface section being associatedto said rearward primary suspension interface and defining a rearwardpivot axis for a rearward pivot arm; said forward pivot axis and saidrearward pivot axis, in said longitudinal direction, defining a pivotaxis distance; and said pivot axis distance being 60% to 105% of saidmaximum primary suspension interface center distance.
 16. A running gearunit comprising: a running gear frame body defining a longitudinaldirection, a transverse direction and a height direction; said framebody comprising two longitudinal beams and a transverse beam unitproviding a structural connection between said longitudinal beams insaid transverse direction, such that a substantially H-shapedconfiguration is formed, each longitudinal beam having a suspensioninterface section associated to a free end section of said longitudinalbeam and forming a primary suspension interface for a primary suspensiondevice connected to an associated wheel unit; each longitudinal beamhaving a pivot interface section associated to said primary suspensioninterface section and forming a pivot interface for a pivot armconnected to said associated wheel unit; said primary suspensioninterface being configured to take a total resultant support forceacting in the area of said free end section when said frame body issupported on said associated wheel unit; wherein said primary suspensioninterface is configured such that said total resultant support force isinclined with respect to said longitudinal direction and inclined withrespect to said height direction, said pivot interface section, in saidlongitudinal direction, is arranged to be at least partially retractedbehind said associated free end section; a forward free end, section anda rearward free end section of one of said longitudinal beams, in saidlongitudinal direction, defining a maximum longitudinal beam length ofsaid longitudinal beam; a forward pivot interface section associated tosaid forward free end section defining a forward pivot axis for aforward pivot arm; a rearward pivot interface section associated to saidrearward free end section defining a rearward pivot axis for a rearwardpivot arm; said forward pivot axis and said rearward pivot axis, in saidlongitudinal direction, defining a pivot axis distance; and said pivotaxis distance being 60% to 90% of said maximum longitudinal beam length.17. A running gear unit comprising: a running gear frame body defining alongitudinal direction, a transverse direction and a height direction;said frame body comprising two longitudinal beams and a transverse beamunit providing a structural connection between said longitudinal beamsin said transverse direction, such that a substantially H-shapedconfiguration is formed, each longitudinal beam having a suspensioninterface section associated to a free end section of said longitudinalbeam and forming a primary suspension interface for a primary suspensiondevice connected to an associated wheel unit; each longitudinal beamhaving a pivot interface section associated to said primary suspensioninterface section and forming a pivot interface for a pivot armconnected to said associated wheel unit; said primary suspensioninterface being configured to take a total resultant support forceacting in the area of said free end section when said frame body issupported on said associated wheel unit; wherein said primary suspensioninterface is configured such that said total resultant support force isinclined with respect to said longitudinal direction and inclined withrespect to said height direction, in said height direction, one of saidlongitudinal beams, in a longitudinally central section, defines alongitudinal beam underside and a maximum central beam height of saidlongitudinal beam above said longitudinal beam underside, one of saidfree end sections of said longitudinal beam defines a maximum beamheight above said longitudinal beam underside; and said maximum beamheight being 200% to 450% of said maximum central beam height.
 18. Arunning gear unit comprising: a running gear frame body defining alongitudinal direction, a transverse direction and a height direction;said frame body comprising two longitudinal beams and a transverse beamunit providing a structural connection between said longitudinal beamsin said transverse direction, such that a substantially H-shapedconfiguration is formed, each longitudinal beam having a suspensioninterface section associated to a free end section of said longitudinalbeam and forming a primary suspension interface for a primary suspensiondevice connected to an associated wheel unit; each longitudinal beamhaving a pivot interface section associated to said primary suspensioninterface section and forming a pivot interface for a pivot armconnected to said associated wheel unit; said primary suspensioninterface being configured to take a total resultant support forceacting in the area of said free end section when said frame body issupported on said associated wheel unit; wherein said primary suspensioninterface is configured such that said total resultant support force isinclined with respect to said longitudinal direction and inclined withrespect to said height direction, said transverse beam unit comprises atleast one transverse beam; said at least one transverse beam, in asectional plane parallel to said longitudinal direction and said heightdirection, defining a substantially C-shaped cross section; saidsubstantially C-shaped cross section being arranged such that, in saidlongitudinal direction, it is open towards a free end of said frame bodyand substantially closed towards a center of said frame body; saidsubstantially C-shaped cross section extending, in said transversedirection, over a transversally central section of said transverse beamunit; and said substantially C-shaped cross section, in particular,extending, in said transverse direction, over a transverse dimension,said transverse dimension being at least 50% of a transverse distancebetween longitudinal center lines of said longitudinal beams in the areaof said transverse beam unit.